The results of a complete thermogravimetric study of copper benzene-1,3,5-tricarboxylate (Cu-BTC or HKUST-1) are reported here together with mass spectrometry (MS) and Fourier transform infrared spectroscopy (FTIR) analyses of the evolved gases up to 800 degrees C. Oxidative and inert conditions were applied to reveal the stoichiometry of the as-received synthesis product. In spite of using a water-ethanol mixture during the synthesis and the filtration, only water is retained in the pores. It is proposed that the thermolytic release of ethanol in the temperature range 150-250 degrees C originates from ethanol-benzene-1,3,5-tricarboxylate (BTC) esters situated on the surface of the HKUST-1 crystal, and which limit the size of the developing crystals during the synthesis. (C) 2016 Elsevier B.V. All rights reserved.